Wireless communication systems for reducing power consumption are known (Patent Document 1). The wireless communication system of Patent Document 1 includes a host, a router and an end device.
The router relays wireless communications between the host and the end device. Each of the router and the end device has a sleep mode and an active mode. The sleep mode is a state where the communication capability through Zigbee (registered trademark) is unavailable, and the active mode is a state where the communication capability through Zigbee is available.
When the end device in sleep mode detects abnormalities in temperature using a temperature sensor connected to itself, it transmits a WAKE-UP signal to the router. When the router receives the WAKE-UP signal from the end device, it transitions from the sleep mode to the active mode and relays wireless communications between the end device and the host.
When in the sleep mode, the router keeps active only two circuits, i.e. the frequency conversion circuit and the wave strength detection circuit, of the wireless circuitry that performs normal wireless communication, and uses these two circuits to detect the WAKE-UP signal.
Patent Document 1: JP 2007-104174 A